Secondary reinforcement for concrete structures.



-R.v B. HA'RIIVIAN. SECONDARY, REINFORCEIVIENT FOR CONCRETE STRUCTURES.

x APPLICATION FILED APR. I5, I9I2, *H Patented July 10, 1911.

4 SHEETS-SHEET I.

MII

el I

R. B. HARTMAN." SECONDARY REINFORCENIEN FOR CONCRETE STRUCTURES.

APPLlcATloN man Amm. i912. v

Patented July 10, 191

4 SHEETS-SHEET 2.

R. HABIA/AN SECONDARY REINFORCEMENT FOR` CONCRETE STRUCTURES.

APPLICATION mso Amis, 1912.

n. HARIMA'N. l y SECONDARY REINFORCEMENT FOR CONCRETE STRUCTURES.

APPLICATION FILED APR. I5. i912.

Patented July 10, 1917.

4 SHEETS-SHEET 4.

RIIDOLPH B. Henri/IAN, or MILWAUKEE, WISCONSIN.

SECONDARY REN'IE"RCEMlllhV` FOR CONCRETE STRUCTURES.

Speccation of Letters Patent.

Patented July l0, lgill?.

Application filed April 15, 1912. Serial No. 690,980.

Y To all 'whom l may concern:

Be it known that l, RUDOLPH B. HART- MAN, of Milwaukee, Wisconsin, have invented certain Secondary Reinforcements for Concrete Structures, of which thel fol lowing is a specication. v

ln my former application, Serial Number 369,763, filed April 23, 1907, which was a division of my original application, Serial Number 288,068, led November 18, 1905, l have disclosed my discovery of some of the reasons for failure in reinforced concrete together with my invention of means for providing` against such failures by a suitable disposition of a small addition of metal and therebypso strengthening the beam or other elements concerned as to enable the same edective resistance to be obtained with a much smaller total quantity of metal than would otherwise be necessary; and the present application concerns a still further development of such means, which will effect a correspondingly greaterl saving of metal. To enable the meaning of this statement, and of the following specification, to be understood, it will be necessary to resume briefly the nature ofthe former invention.

The stresses in any structural element subjected to tension, compression, lieXure or any other stress are, as shown and set forth, for example, in the Bulletin of the University of Wisconsin :ll-148 Engineering Series, volume 8 No. 4E, pages 819 to 394, of an extremely complex nature and by no means of the simple and unidirectional quality which has heretofore generally been assumed by engineers. This, of course, is true as well for concrete as for other materials, but for reinforced concrete it is still further complicated by the discreteness or discontinuity of the material. Ve are here dealing with a material having a high tenacity embedded in and more or less united with another material. having a very low resistance in tension but a considerable resistance in compression. lt has been customary in calculating the strength of structural elements to assume a tensile strength of the metal equal to the safe load which would' be allowed it were the metal used alone; yet, as a matter of fact, this assumption is utterly fallacious and false, for the reason that circumstances never permit the metal to reach the maximum safe loading which is allowed to it by the constructor. Long before such a tensile stress is kreached the breakage of the metal, viz. by the `releasing its hold thereon; or in other beam fails in another manner than by the concrete words, the concrete breaks away from the metal and acts separately. lt will be obvi' ous that it is useless to reckon on a larger tensile strength for the metal than that at which the concrete can retain its grip there upon.

The initial failure of the concrete is found to be marked by a network of microscopic or ultramicroscopic cracks, which mark the surface along which, with any further stress, the concrete will fail; and my former invention, hereinabove referred to, consisted briefly in providing a secondarymeshwork of metal in the neighborhood of the reinforcement which serves to prevent the formation and extension of these cracks, or in other words acts to uniformly distribute this secondary stress through the concrete, the uniform distribution of which leads to the formation of these cracks. This secondary reinforcing meshwork, by preserving the integrity of the concrete i1ninediately adjacent to the main reinforcing bars, serves to preserve the grip of the concrete upon the latter and therefore to permit the transferring to them of a much higher portion of the main tensional stress than would Otherwise be possible.

lt is the object of the present invention to improve the disposition of the secondary reinforcement over that heretofore disclosed byme, and more particularly by completely inclosing the reinforcing rod in. a secondary reinforcement which may be a meshwork or a circular metal coil adapted to combine the concrete and prevent its flow away from the rod. This is entirely independent'of and distinct from the circular or ring-reinforcement of columns, which has been heretofore used surrounding the reinforcement bars as a whole and alleged to prevent flowage of concrete from the center of the column toward the outside.

l further aim by my novel construction to provide practical means for supporting the primary or secondary reinforcing elements in proper relation to each other during construction.

l further aim to provide special means for supporting narrow concrete slabs and beams by a special arch or Compression reinforcement.

My invention further comprises the par 25" n klshowing the rmam vreinforcements thereof as '#amples' of my forcement as applied to a lsingle rod; A

5 to l() inclusive are diagrammatic ticular constructions and combinations of described and more par-y 1er tension; Y

Figs. 3 and 4 are side views of other eX- improved secondary .rein- Figs.

transverse sections of other forms of my im- 'lproved secondary reinforcement;

Figs. 11 and 12 are respectively a front "view and an axial section of ya spider or vsupport for centering the .secondaryV reinforcement with respect to therod;

Figs; 18, 14,15 and 16 are transverse sections of forms for reinforced concrete beams,

'provided with various dispositions of secfond'ary reinforcements;`

` Figs. v17 andlS are transverse sections of columns showing the application of my imf-proveinent to the reinforcement thereof;

ment in the case of a Y'truss-frame of Fig; 19 is a longitudinal section `through fa beam or yfloor-slab, illustrating the application theretovof my secondary reinforcecompression-rod Fig. 2O is a' longitudinal section through another form of the same; v

Figs. 21 and 22 are respectively a longi- 2tudinal central section and a plan-view through an a'reh Vor truss-frame for beam for Fslab-reinforcement;

,'7=Fig. 23 is a transverse section of the Figs. l #and 21 taken on plane 23; v

Figs. 24 and 25 illustrate in plan and in transverse central section onthe vplane 25 Vfa"truss-frame or disposition of arch-bar reinforcements for a floor-panel;

Fig. 26' is a plan-view of another arrangement 'of arch or -compression-reinforcement for ioo'r' panels; A

lFig. 27 is afragmentary transverse secltion ofthe same on the plane 27 thereof;

Figs. 28 and 29 are Acentral transverse 'sections respectively of the top-halfand bottom-half of one of the rod-'holding spiders of Figs. 24 and 25';

Fig. 30 is a plan view of the element "shown in Fig. `29 5 Fig. 31 shows the central-portion of another forml of compression-reinforcement for e' n Figs-@32 to'35 inclusive, yare av floor-panel;

perspective views, somewhat schematic, of different ar- "rang'ements showing my secondary reininabove referred to 1forcement) .of outward How of the concrete, which outyany ofthe forms of Figs. scribed) may simply be :rods a or-they maybe strungupon the stirrupf inthe case of a wire-mesh. It will be In these drawings the same reference vcharacter refers to the same part wherever used.

My secondary reinforcement embodies in its simplest fo/rm a combination with the main reinforcement-rod a of an enveloping network or hoop-reinforcement, which in Figs. 1 and 2 is shown as a cylindrical wircmesh b; in Fig. 3 as a helically turned rod or wire c; and in Fig. 4 as a combination d oftwo such helically turned wires or rods, forming substantially a meshwork whose meshes are oblique to the axis. Although shownv in Figs. 1 to 4 as cylindrical, it is not necessarily so, as it may assume an elliptical form a polygonal form b2, a square form 3, a triangular .form Zi, a looped form Zf, or a cardioid form 7), as shown, by of example merely, in Figs. 5, 6, 7, 8, 9 1() respectively. In Fig. 5 I have also shown by way of example three rods a laid side by side, and in Fig. 18 three such rods grouped together. The essential feature 0f all of these is that the individual rod or group of rods is completely inclosed by the secondary reinforcement in such manner as to accomplish two things: first, a Auniform Vdistribution of the contractile stress upon the rods, thereby preventing the cracks here- (which was partiallyaccomplished by my former form of the reinand secondly, the prevention ward iiow is known to be a conspicuous factor in the failure of concrete members under compression, and which I `have found is also a factor in the failure of that portion of a concrete member which contains metal rods under tension, such outward flow tending to weaken the hold of the concrete upon the rod.

'The secondary reinforcement may accom- Yplish athird object as illustrated in Figs. 13.

14, 15 and 16, which showthe disposition of vthe reinforcement-rods al in a beam-form comprising a bottom c and sides c?, said rodsl a being supported by suitable means such as a stirrup f. In this case the reinforcing cages 7) (this letter here symbolizingl 1 to 10 above dehung -upon -said rasante noted that in this case the reinforcing cases t may rest upon the rods a, and therefore it is not necessary that the latter be out of contact therewith, and as a matter of fact this may conceivably be a better disposition than the one where trically with the rod, because the .principal direction of the liow of concrete would be toward the nearest side of the beam, to wit the bottom thereof, and therefore the greatest protection of the secondary reinforcement should be exercised upon that side. rIhus the problem is solved of readily and easily supporting the secondary reinforcement, which was left unsolved in my former invention hereinbefore cited.

In addition to the above-mentioned objects a fourth obj ect may be accomplished by the secondary reinforcement as this is shown in Figs. lll, 15 and 16, which represent di'erent forms of laterally deployed mesh-work, which provides simultaneously a secondary reinforcement and also a supporting and spacing means for the rods, and enabling me to dispense with stirrups f or similar supports. In Fig. 14: the secondary reinforcement comprises a plurality of laterally deployed helical wires g, between any twoV successive links of which are formed spindleshaped openings through which pass the rods a.. In Fig. 15 the wires h extend transversely in a series of continuous joined cardioid forms having central loops h in which hang the rods a, thus spacing them apart from the sides of the reinforcement. In Fig. 16 is shown a plurality of longitudinally disposed helical wires c, the same as in Fig. 3, the coils of these wires, however, interlocking to form spindle-shaped apertures or passages through which are inserted the rods a, and a second row of rods a may rest in the spandrels over the coils, as shown.

For keeping the secondary reinforcement cage t in proper relation to the reinforcement bar which it protects, I may provide any suitable device, such as the ring-spacer shown in Figs. 11 and 12, having a perforated hub e through which the bar a passes and a rim z2 adapted to pass through the cage t.

In Figs. 17 and 18 are shown cross-sections of a round and a square column respectively, each of which has longitudinal main reinforcements al (each of which may consist of a single rod or a group of rods) each inclosed in a secondary reinforcementcage b, which may be any of the forms shown in Figs, 1 to 10, and the usual ring-reinforcement e', which incloses the column as a whole. It is to be understood that my secondaryreinforcement, while it takes a ringform, is wholly independent of the reinforcement provided or intended to be provided by the ring-bars i, which are properly a main reinforcement, whose function or supposed the cage is disposed concensuch use would bc impracticable.

function is to vcheck the outward flow 'of concrete due to the compression of the column en masse, and has nothing to do with the maintenance of the integrity of the concrete or the prevention of fiowage from the individual rods.

As I have hereinabove stated, the second ary action which results in radial and tangential stresses with respect to the individual reinforcing rods takes place whether the rod be in tension or compression, but it is Agreater where the rod is in compression, because here the endwise en mf/.ssc compression of the concrete is added to the secondary stress and in the former case is subtracted therefrom. I-l'ence my invention is especially useful in cases where the metal is used to sustain compression. I have found that in some cases metal compression-reinforcements can be used to good advantage where assisted by my secondary reinforcement, where without it An instance of this is shown in Fig. 19, which illustrates in section a shallow beam or floorslab in a case where the depth is narrowly limited by structural cxigencies or requirements of the building-specification. In this case the floor or beam may be so shallow that it is incapable of self-support without a compression-reinforcement; but the support of reinforcing rods at exactly the proper distance from the upper surface of the beams or slabs is a practical problem which, to the best of my knowledge, has not yet been solved. It will be understood that if the rods are too high, or are close to or project above the surface, their function as compression-rods will be impaired or nullified, since they will have no hold on the concrete, while on the other hand, if they are too low, their function as compression-rods is again impaired, and the amount of sag which will suffice to nullify their function will of course be very small on a shallow beam or slab. Furthermore, the l such rods at the top of the beam or slab is a very different one from that at the bottom, because all he concrete has to be poured over and sink between them, and this and the running of carts and men over the unnished floor makes it impractlcable tomantain them without displacement; but when provided with my secondary reinforcementcage, the exact position of the rods becomes less a matter of consequence because of the 12e action of said cage in reaching out, so to speak, to the surrounding concrete beyond the rod itself and uniting it thereto and therewith.` If the rod isabove its proper position the cage `unites it to the concrete below, and if it is below its proper position, the cage unites it to the concrete above.

' A further` development of this idea of forming a means of support for compression-rods at: the proper elevation is illusproblem of supporting 11u Vltrated .in 20, in .which the` compressionrod .7c is .convexed .upward or arched, as

y shown, Aand it 4may kbe given .exactly the placed ffor v-may be bound to theendsofa tension-rod proper amount of bendtoihold its shape by vIi'tself .and thus rest with itsends upon the column rods or some other suitable'support it; or, on-'the other hand, its ends l .whichextendsstraight along the bottom x Y .to give the rod Icapermanent bend, but

'it is placedjn frod 'Z 1and-.aft .rodsformf together. a simple varch-truss form,

killustrated inzFig. 21. I Vjoint between the 'rods f socket-casings m, -as 4set-.screws ,mf

"(wliicli may extend angle to each other, of the rods/eA of. adjacent spans. It willvbe of the beam,;in whichy case it is not. necessary azjig or'form along withthe er uniting itthereto, the two prefer=tomake the .and Z by suitable provided with means such Vforclamping the .rod Z farther to the next span) and l a .pair of `sockets/11??, disposed at `an for receivingtheends observed 'that the-member m forms asort of Labutment for the rodk, and even 4where .there is. no similarrodl on.A the adjacentlspan ytotake the-thrust of therod -cjthe empty socket on the casting .m .presents a :large surface to -the concrete transverse Ito lthe direction ofthrust. The socket and. abutment-member m'may also be used where. the

rodsl 7c. are merely bent Aas hereinabove .sug-

., said ...clips being .76, aswell as the rod provided withy the` secondary reinforcement Vthe formation offa whole l illustrated; .inf Figs.v r24, .and 25, theflatfor beamless system of 3.135.h

.gested and the rods Z. are omitted. The rod *Z,.may or may notibe cagev Z) .as shown.

Figs. 21, 22 .and 23 inclusive illustrate a form.- of compression-barframe suitable for beamsand. slabswhich is adaptedto stand Y alone. upon theform without further support. A pair of arched or compression-rods k', which are bent in lan angular shape, are united `at their. middle. and ends by clips n `and..0,.and a. third straight bar'Z,I disposed midwaynbetween the bars 7c', `.is `likewise united. thereto r-frictionally by lthe clips n, ...preferably made in two halves n divided along the axes of the bars and Zand lprovided-with,shallow semicylindrical recesses which, when the two v 5o .h

l form sockets for said bars 7s. and Z in which .they .are frictionally secured. 1 Clipo is Vlikewisemade .in two Vhalves 0 (see alvesare clamped together by the` bolts n2,

The middle Fig. .23) but has only two `such sockets,and thel bolt 02 Awhich'holds the twoghalves to- .,gether, asshownin Fig.l 23, may extend downwardlyand be provided with a hooked f end o.3 .engaging the Vmember Zmidway of 'the latter and thus -forming a medial joint between: the three elements.

H"lhesame.principlemay be extended to floor-panel, vas especially in construction, :where.-.veryxy thin slabs are '.desired. fFig. 24

.represents .a yiioor =flooii,.supportedby columns p andbouiided zb, Vwalls or ibeams p on two sides only, .wherefrom .it will be readily `arms of said spider, as shown.

abutment faces s4, .wheirthefhahes are' united, as by a central ibolt ffore slightly into.` the. metal. The

. ets. Theform of the observed, such as to distribute fiayaaeee panel. at one corner of a apparent how ythe same construction may be applied to a flooring-panel;bounded onA all sides by beams ,or on one. or no sides. Fig. 25 shows a` transverse sectionthrough theiframe and Hoor on the medial plane 25. I provide over each columna `radial armed spider, such as g, r .and s, according as the panel is on the corner, onoHeedge, or in the middle of thel floor; ,and the .upright colunin-reinforcement-bars maysbe. so disposed as to pass between the Correspondingly, in the center of each panel midway betweenthe columns, I provide an eiwht- .armed spider s. As shown in thev detailed yiews,.Figs. 28 to 80, the spider s isforined v.intwo parts, s andsg, divided by the axes .of the reinforcing rods along a conical or pyramidal surface, said halves having semicylindrical recesses s3 therein, terminated by said recesses forming,

si passed, through holes s therein, sockyetsfor the ends of the rods t and t.

VIn order to gripthe ends of each of the rodsin its. socket, each of the semicylindrical recessessi may-have on itsifree end a snug `or projection 87, which makes the normal sizey of the entrance to the socket theresmaller than the size of the rod, whereby in gripping up the several .rods the individual arms are caused to yield and. press frictionally upon the sides of each .of theniembersyt. and t and thus hold it in its place, and if necessary the snugs S7 may be given thereby enough .edge to bite socket-castings g and 1' may be formed in the saine way as the socketpiece s Vwith the unnecessary arms omitted; or the sainecastings s. may be used in place of the members. g and i", leaving empty sockinember .s is, it will be the endthrust of the rods` radially over a wide area inthe concrete. The sockets s over the column-ends are, of course, disposed with the apex downwardly, and those between the. columns with the apex upwardly as shown inFig. 25. .In addition to the arch- V.reinforcement bars t, which extend diagonallyfrom'the columns to the center of each panel, straight tension-bars u are employed extending from column to column and forming ties for the thrust of the compression-inembers t; and also compress1on-bars they, are connected Lby clips av (as iniFigs. 26 and 27), or socket-pieces o and o', as shown. The

lateral thrust of the bars t is taken by bars u parallel tothe bars u bars u at their crossing point.

and immediately under the bars t', and the bars a may be tied to the middle socketmember s by an extension on the bolt 85, which has a hooked end ss engaging the two The vertical thrust which is transferred by the larch-bars t from the center to the side of the panel, is in its turn transferred to the columns in cases where there is no beam, wall or other support immediately below it, as in the beamless construction, by means of secondary arch-bars u2 which are disposed immediately over the bars u and are connected to the ends thereof by clips e', and support the bars tf by suitable suspenders; for example, the bolts v2 which unite the two parts of the clip e may be replaced by a U-bolt o3 passing over the arch-bar u2 as shown. 'Io avoid unnecessary complexity of the drawing the secondary arch-bar u2 is shown only in one place, on the right of Fig. 24, and in section on the right of Fig. 25, and it is shown as broken at one point and the ends turned aside to show the bar u directly under it.

rl`hus I provide a very strong and rigid thrust-framework, without the use of anything but plain bars and a few simple castings. The ends of the reinforcing-bars may, of course, where desired, be threaded into the castings, but this, on account of the extra labor `involved in screwing them up, I consider inadvisable in most cases.

Another simple form of thrust-framework for floor-panels, adapted to stand alone and involving nothing but plain reinforcing bars and common U-bolts, is shown in Fig. 26. Here the diagonal rods fw span the panel in pairs from column to column, as shown, and one rod fw isshown bisecting each angle between the diagonals. Tension-Y rods here are not shown, and may be used or omitted as desired. The rods w and fw are` of course, bent convexly as in other cases, and at their meeting-points are secured to each other by U-bolts or stirrupbolts :n having plates m', or any other simple form of clip.

In Fig. 3l is shown a similar structure to that of Fig. 26, provided, however, with the rods fw in pairs instead of single, and the whole united by clips or U-bolts fr at the meeting points as before.

My secondary reinforcing-cage is particularly adapted for use and serviceable in the case of other than plain cylindrical bars, and yfor deformed bars of any kind, in which, as is well known, the unequalV radius of surface-curvature'produces in the inclosing concrete unequally distributed stresses, which therefore tend to produce cracks in said concrete more readily than they are produced in round bars. In such cases therefore, my secondary reinforcement-cage l counteracts this effect and produces a redisrods.

tribution of the stress which largely neutralizes the bad effect of corners and angles on the surface of the reinforcing-member.

By way of illustration there is shown for example in Fig. 32 a twisted bar a', in Fig. 33 a corrugated bar a?, and in Fig. 3e a T- bar e3, in Fig.v 35 a channel-bar at; surrounded in each ease by a secondary reinforcingcage l), which may be of any of the types illustrated in Figs. l to 10.

Structural shapes such as I-beams, Ts and channels are also especially adaptable for use in connection with my compressionreinforcement-frame-construction. have illustrated one example of this in the draw-V ings, Figs. 36 and 37. This frame comprises eight T-bars a5, a, extending radially from the center of the panel and united together by a gusset-plate s by means of rivets 81 or other suitable fastenings. Said bars are asshown in Fig. 37 concaved downwardly or arched, and to take up the end-thrust of said bars, as well as act as direct tension reinforcements for the concrete, a set of tierods a3 are provided. It will be seen that a tie-rod extends in two directions from the end of each intermediate arch-bar a to the ends of the main arch-bars a5 diagonally opposite, thus providing four V-shaped tie- 'lhe ends of said tie-rods are structurally united to the ends of the main archbars, a convenient fastening consisting of a yoke-casting uf provided with set-screws M5, said casting being notched in the form of a member having an eye through which the two arched ends are adapted to pass, and after drawing them up to the requisite tension, they are clamped fa st by the set-screws M5. The two rod-ends will then be as shown in the upper left-hand corner of Fig. 36, andto secure'them in this position and prevent them froin pulling out when the stress comes upon them, they are spread apart as shown in the other three corners of the drawing. The frame as thus far described is self-contained and complete for most purposes and the additional features shown are optional or to be used in certain cases only. The panel-frame may be partially set up and riveted in the shop, and the riveting and addition of the tie-rods completed on the job; after which the frame as a whole may be set in place and the concrete poured. It will be noted that the tension-bars 'l1/8 form avery complete tension-reinforcement for the concrete in the panel; and they may also form, additionally, a support for other tension-bars laid upon them.

In some cases, I may provide additional tension-rods connecting the ends of oppositely extending bars a5 and a", in the positions indicated by the dotted lines extending in the centers of said bars; and instead or in addition to such rods, I may employ girth tension-rods us, which as a whole extend around the panelframe, passingover theends of the main arch-bars a5 and engaging in notches inthe flanges thereof; each separate bar being L-shaped and screwthreaded at the ends and united to the adjacent bars by .turnbuckles uf'. The ends of the intermediatearch-bars a may also rest upon@ these tension-rods (which also actas tensioli-reinforcements for the concrete), the flanges thereof being notched out as shown. at a7, Fig.` 37,to receive these rods u as.l well as the rods as. If further support for the' verticalstress upon the intermediate archebars a4 is' needed, it may be provided by secondary'arched T-bars as, extending between adjacent corners of the panel and each connected with the end of the correspondingibars aby a suitable suspender, as, foreXamp'le-a Uebolt v1 extendingunder the barsu' andi ue andI having its ends passing through andiV bolted over a strap-plate o5.

e secondary arch-bars as may have their ends 'joined to theV ends of the main-bars a5 by gusset-plates s to which both are rivetedf,I asshown on the right of Fig. 36; or they may be independent bars as shown at lthe bottom of Fig. 36; or they may be arched frames like those shown in Figs. 2.0` and 21. The gusset-pl`ates 8.", s are preferably perforated on various points of their area as shown,l to] give bending-necks for the concrete on their opposite sides.

In all' these forms the secondary reinforcing-cage b, as shown on some of the rods inv Fig. 24, will bea useful adjunct but is not essential to my invention.

Instead of a ring-spacer e shown in Figs. 11 and 12, asim'ple'r device for holding the secondary reinforcement in place consists of three wires a3 twisted together as shown in Fig. 38.- All of the threeA wires are somewhat longer than the diameter of the 'secondary-cage Z) or c.. The ends of one wire being twisted with one end of each of the other' tworwires and around the wire of the secondary-cage, the two free ends of said last-named wires are left open until the rod a has-been put in place and then they are twisted together and around the wire of Ythe cage cV the same as the other tWo ends,

forming a Y-shaped spider. It is clear that this is applicable to either the Wire-mesh or the simple helical-wire form of cage, and especially so to the latter, as the wires a3 can be manipulated between the coils of the Wire'. Y

Copies vof this patent may be obtained for ve cents each, by

While I have hereinabove shown the most improved! forms ofl my invention, I wish it understood that not all of the features are essential` thereto or necessarily made in the exact forms shown, but various changes and:y modifications in the constructions as hereinl shown may be made without departing fronr the spirit of my invention, and I wish it understood therefore that the latter is not otherwise limitedv than by the scope of my claims.

Having thus described'my invention, what claim as new and desire to secure by Letters .Patent is:

l. In a structural member of reinforced concrete the combination of a plurality of main reinforcing members and a secondary reinforcing cage inclosing and closely paralleling the surface of certain of said individual members, whereby the secondary reinforcing cage incloses all of the concrete which is in immediate juxtaposition with the corresponding main reinforcing member, and binds it together into a unitary mass and gives it au increased hold on said reinforcing member.

A2. In a structural member of reinforced concrete, the combination of a plurality of main reinforcing members and a secondary reinforcing cage inclosing and closely paralleling the surface of certain individual main members, said secondary members consisting of metallic wire of smaller diameter than said main 'reinforcing members.

3. In a structural member of reinforced concrete, the combination of a plurality of main reinforcing members and a secondary reinforcing cage inclosing and closely paralleling the surface of certain of said individual members, said cage comprising a wire mesh-work.

4. In a structural member of reinforced concrete subject to transverse or flexural stress, the combination of a plurality of metal reinforcing elements, each having surrounding it a cage constituting a secondary reinforcement; said cage having a Wire extending helically around said element.

.In witness whereof I have hereunto set my hand in presence of two witnesses.

RUDOLPH B. HARTMAN. Witnesses Washington, D. C. 

